Reverse magnetron with slot mode absorber



1966 M. F. uscxo 3,231,781

MAGNETRQN ed Sept. 15, 1962 3 Sheets-Sheet 1 INVENTOR. MAURICE F. LISCIO 2; f%@

ATTORNEY Jan. 25, 1966 M. F. LISCIO 3,231,7s1

REVERSE MAGNETRON WITH SLOT MODE ABSORBER Filed Sept. 13, 1962 5 Sheets-Sheet z FIG.4

INVENTOR.

MAURICE E. LISCIO ATTORNEY Jan. 25, 1966 Filed Sept. 15, 1962 FIG.5

M. F. LISCIO REVERSE MAGNETRON WITH SLOT MODE ABSORBER 3 Sheets-Sheec 5 INVENTOR. MAURICE E LISCIO ATTORNEY United States Patent O 3,231,781 REVERSE MAGNETRON WITH SLOT MODE ABSORBER Maurice F. Liscio, West Grange, N.J., assgnor to S-F-D Laboratories, Inc., Union, N.J. a corporation of New Jersey Filed Sept. 13, 1962, Ser. No. 223,499 9 Claims. (Cl. 315--39.53)

The present invention relates in general to the electrou dscharge devices of the erossed electrie and magnetic field type and more specifically to a reverse magnetron useful for generating high power microwave energy at extremely high frequencies such as required in high power, high resolution radars.

A reverse magnetron tube typcally comprises a -circu- 1ar electric mode cavity or circular electric mode wave propagating structure surrounded by a circumferential array of outwardly directed vane or cavity resonators coupled to the excited circular electric structure via a circular array of axial slots communicatng with alternate anode resonators. The array of anode resonators are surrounded by a magnetron interaction region formed by an annular cathode emitter ernitt in g radally inwardly into the anode, in the presenceof a strong axial magnetic field. Rotatng spokes of electron space charge interact With the 1r mode fields of the anode resonators to excte the circular electric mode in the circular electric mode cavity. Sinee the stored energy of the circular electric mode cavity is much higher than that of the vane resonator eircuit the anode vane resonator system s locked in the 1r mode to the circular eleetrie cavity mode thereby stabilizing the magnetron. The reverse magnetron struoture may be used as an osoillator or as an amplifier and microwaveenergy is extracted from the circular eleetric mode wave propagating structure or cavity and fed to a suitable load.

Heretofore a reverse magnetron of the above described type has been bu1t operating at approximately 35 gigacycles and generating a peak power of approximately 150 k-lowatts With an average R.F. power of 75 watts. When an attempt is made to obtain this performance on a reproducible basis several severe problems are encountered Which prevent attaning these specifications.

Some of the problerns associated With achieving the power output of the prior art reverse magnetron on a consistent basis are as follows: Tube assembly by press fitting the cylndrical slottd anode assembly into an annular or ring-shaped slot mode absorber, carried from the tube body, often results in distorting the anode and losing the required concentricity between the anode and the eathode resulting in catastrophic failure of the tube -in use; also the slot mode absorber ring reduces efficency of the tube by excessively coupling to the desired electrc fie1ds of the anode resonators; thermal deformations of the tube body zind anode assembly eneountered during tube assembly welding operations and in tube use, respectively, produce scalloping of the anode resonator array causing catastrophic failure of the tube in use, also the cathode end hats increase the magnetron axial magnetie gap length resulting in excessive magnet size and weight.

The reverse magnetron tube of the present invention solves the aforementioned diflficulties associated With the prior art tube and provides a 32-35 gigacycle magnetron having a peak power output in the order of 290 kilowatts With verage power output of approximately 50 watts while yielding overal1 effi-ciencies of approximately 30% and a tunable bandwidth of 12%. This tube represents more than an order of magnitude increase in peak power output With approximately double the previously obtained eficiency While having a long operating life in excess of 2,400 hours.

The principal objeet of the present inventon is to provide an improved high power reverse magnetron tube yielding substantially enhanced peak power With increased efleiency and operating life.

One feature of the present invention is the provision of a lossy slot mode suppressor element having a portion axially coextensive of the coupling slots and said mode absorber being carried from the slotted anode wa1l whereby concentricity of the anode wall and the mode absorber are maintained during tube assembly thereby preventing distortion of the anode wall Which otherwise results in eatastrophic failure of the tube.

Another feature of the present invention is the provision of a slot mode absorber disposed axially coextensively With and adjacent the coupling slots, said slot mode absorber extending inwardly from the ends of sad slots toward the centrally disposed anode resonators and said slot mode absorber element decreasing in thickness toward the end thereof adjaeent the anode resonators for minimizing dissipation of wave energy of the de-sired anode mode in the slot mode absorber.

Another feature of the present inventon is the provision of an evacuable tube structure wherein an anode structure which is surrounded by a relatively rigid tube envelope is made free to expand a substantial distance in the axial direction in a substantially unrestrained manner With respect to the relatively rigid surrounding tube envelope to prevent axial compression With consequent deformation of the anode structure leading to loss of concentricity between the anode structure and an adjacent cathode structure encountered during tube assembly and use whereby catastrophic failure of the tube is prevnted in use.

Another feature of the present invention is the provision of a reverse magnetron having an axial gap between the anode strueture and the tube permitting the anode to operate at a potential independent of the tube envelope, including the magnet pole pieces and cathode whereby the cathode end hats may be eliminated thereby reducing the axial magnetic gap length and consequently the magnet size and Weight.

Other features and advantages of the present invention Will become apparent upon the perusal of the specificaton taken in connecton with the accompanying draw-ings wherein:

FIG. 1 is an outside perspective view of the reverse magnetron tube of the present invention,

FIG, 2 is an enlarged fragmentary cross sectional view partly broken away of the structure of FIG. 1 taken along the line 2-2 in the direction of the arrows,

FIG. 3 is a fragmentary view partly in cross section and partly broken away of the portion of the structure of FIG. 2 taken along the line 3-3 in the directon of the arrows,

FIG. 4 is an enlarged radially foreshortened cross sectional view of the portion of the structure of FIG. 2 delineated by line 4-4 and rotated to the right, and

FIG. 5 is a longitudinal cross sectional view similar to. FIG. 2 of; a reverse magnetron employing alternative features of the present invention.

Referring now to FIGS. 1, 2, and 3, character 1 represents the hollow tubular supporting body of the reverse magnetron, as of copper, to whch other parts are braied. or otherwise suitably fastened to form a structure capable of being evacuated. On opposite sides of the body 1 in axia1 alignrnent there are brazed to the body 1 a tubular output waveguide assernb1y 2 and tuner 'assernbly 3. Cathode lead-in insulator structure 4 extends outwardly from the main body of section 1 in quadrature With the axially aligned output waveguide and tuner structures 2 and 3, respectively.

The terrn circular electric mode cavity as used heren is defined to mean a cavity formed, dimensioned and excited in such a manner as to support, at its certain prese- Iected operating frequency, a certain crcular electric mode, of the general form TE to the exclusion of other modes. A circular electric mode cavity typcally includes an outer cylindrical side wa11 and may or may not have an axially directed center conductor.

A circular electric mode cavity 5 is disposed centrally of the anode body 1 on the ax-is of the tube. In amplifier embodiments of the present invention the circular electric mode cavity 5 is replaced by a circular electric wave propagating wave structure such as, for example, a hollow cylindrical pipe having an input port as well as an output port. A circumferential array of outwardly directed vanes 6 surround the ercular electric mode cavty 5 and form an array of anode resonators by the spaces between adjacent vanes 6. Alternate anode resonators are electromagneticaliy coupled to the crcular electric mode cavity 5 via an array of axially directed slots 7 communicating through the common wal1 between the anode resonators and the eircular e1ectric mode cavity 5. A magnetron interaction region 8 surrounds the outer tips of the vanes 6 and is defined by the space inbetween the vanes 6 and a surrounding cathode emitter ring 9.

A strong axial magnetic field as of 12,000 to 15,000 gauss for the magnetron interaction region 8 is provided by a bowl-shaped magnet 11, only partially shown in FIG. 2, enveloping the anode body portion 1 and having a reentrant internal magnetic gap extending in the axial direction through the magnetron interaction region 8 between the magnetic pole peces 12 disposed on opposite sides of the anode vanes 6.

Tuning of the tube over its approximate 12% tuning band, centered at approximately 34 ggacycles, is obtained by means of axial translation of a combined cavity end wall and output coupling plate 13 carried upon the end of an axially directed and positioned rod 14 Which is axially translatable via the intermediary of a captured nut 15 and bellows assernb1y 16, partially shown. This tuner and load coupler from the subject matter of and are claimed in copending application 216,228, filed August 10, 1962, and assigned to the same assignee as the present invention.

The negative cathode potential of approximately 23 kv. is appl-ied to the cathode emitter 9 via high voltage lead-in insulator assembly 4. The cathode 9 uses a 10W voltage A.C. filament heater and therefore a dua1 Wire cathode lead-in 10 is used.

In operation, the 1r mode of the magnetron interaction region is locked to the circular electric mode resonator 5 via the intermediary of the coupling slots 7 serving to drive the resonator 5. A11 annular slot mode absorber 24 is juxtapositioned the coupling plate end of the slots 7 and suppresses the undesired slot mode. Output energy from the resonator 5 is extracted via the coupiing plate 13 and transmitted to the load, not shown, via the intermediary of the crcular e1ectric mode output waveguide structure 2 and output wave permeable wndow 17.

The tube structure and mode of operation Will now be described in greater detal as it specifically relates to each of the before-mentioned features of the present invention.

The novel slot mode absorber support feature of the present invention is characterized by the slot mode absorber 24 being carried from the slotted anode Wall and can be more easily seen by reference to FIG. 4.

, In this embodiment the annular slot mode absorber 24 is carried from the free end extremity of the cylindrical anode wall 19 via the intermediary of a I-shaped cross section annular channel 35. The innermost wa11 32 of the annular channel has a longer axia1 extent than the outside wall 36. The channel 35 serves to capture both the anode wa1l 19 and the mode absorber 24 between the side walls of the I-shaped channel 35. The anode wa1l 19 is provided With a plurality of peripherally spaeed radial bores 37 disposed in registry With a plurality of peripherally spaced radially directed bores 34 in the annular slot mode absorber 24. The anode wall 19 and mode absorber 24 are captured together via the intermediary of a plurality of pins 38 as of Monel inserted Within the registered bores 34 and 37. The outer wall 36 of the J-shaped channel has inwardly crimped tabs 39 in registry With the .holes 34 in the mode absorber 24 to thereby fixedly secure together the subassembly including the I-shaped channel 35, anode wall 19, mode absorber 24 and pins 38.

In a typical example of a mode absorber support assembly for a tube operable in the 34 gigacycle frequency range, the slot mode absorber 24 has a thickness of approximately 0.046", is made of a carbon impregnated alumina cerarnic With an axial extent of approximately 0.405 and there is provided approximately a 0.001 cold clearance between the outside diameter of the anode wall 19 and the inside diameter of the slot mode absorber 24.

The advantage of supporting the slot mode absorber 24 from the anode Wal1 is that the mode absorber 24 may be assembled onto the anode wal1 before the tube is assembled thereby assuring that the proper concentricity is maintained between the wall 19 and the mode absorber 24 without introducing any distortion into the cylindrical wall 19. Distortion was previously encountered in the prior art design wherein the mode absorber 24 was carried from the body of the tube and the tube was assembled by axialiy sliding the anode Wall 19 into the center of the annular slot mode absorber 24. With the prior art design the proper axial alignment and concentricity was often lost resulting in physically distorting the anode wa1l 19 and its vane resonator stnucture 6 resulting in catastrophic failure of the tube in use.

In a preferred embodiment of the present invention the annular slot mode absorber 24 is tapered in thickness With decreasing thickness toward the end thereof toward the system of anode resonators. The taper is preferably further arranged such that the removed thickness of slot mode absorber is on the side of the absorber adjacent the free ends of the anode vanes 6 such as to keep the mode absorber 24 close in to the slots 7 and out of the strong electric fields associated With the tip ends of the anode vanes 6.

In this manner the mode absorber 24 does not excessively couple to the desired fields of the anode resonators while still providing suffcient coupling between the slot mode absorber 24 and the electromagnetic fields associated With the slots 7. A1so the end of the slot mode absorber 24 extending toward the vanes 6 extends slightly in the axial direction past the end of the slot cover 32 as of of a wavelength to reduce the shielding of the slot mode absorber 24 by the slot cover 32.

In a typical exarnple of dirnensions for a slot mode absorber for a 34 gigacycle reverse magnetron, the thickness of the slot mode absorber 24 at the vane end thereof is approximately 0.010" and the axial spacing from the end of the mode absorber 24 to the adjacent edges of the vanes 6, where they join the anode wall 19, is approximately A of a wavelength.

In operation, the slot mode absorber 24 serves to heavily couple to the electromagnetic fields associated With a resonance of the slots 7 to prevent sustained oscillaton of the slot resonant modes, while not appreciably absorbing energy from the desired circular electric cavity mode being coupled via the slots 7 to the array of anode resonators 6. If the absorption of energy from the slot mode is insuficient, such that these modes sustain oscillation, the operation of the tube is unstable as it will resonate in the slot mode at a different frequency than the frequency of the circular electric mode cavity thereby causing the tube t0 shift off the desired frequency,

The novel anode wall support structure feature Which readily facilitates unrestrained axial movement of the anode wall 19 With respect to the relatively rigid tube body 1 Will now be explained in greater detail by reference to FIG. 4. The cylindrical anode wall 19 is fixedly secured in a rigid manner as by brazing to the relatively rigid tube envelope 1 at the opposite end from that adjacent the mode absorber 24. At the mode absorber end of the anode wall 19 there is provided a substantial axal gap 41 as of, for example, 0.020 01 0.051 in axial extent. This axial gap 41 permits unrestrained relative axial movement between anode wall 19 and the relatively rigid remaining portion of the tube body 1.

During the tube assembly process circumferential welds are made at joints 42 and apparently due to the high localized heating produced by the welding process the transverse headers 43 and 44 which straddle the anode wall 19, and deformed in such a manner as to cause an axial compression of the interior centra-l portion of the tube body and in particular anode wall 19. Heretofore the prior art anode wall 19 had been fixedly secured to the tube body at one end and substantially press fitted against the tube body at the other end With substantially no axial gap 41. During the welding process inward axial translation of the central portion of the tube body caused the rather fragile slotted anode wall 19 to be compressed from the ends thereof resulting in a central bulging deformation of the wall 19 and circumferral scalloping of the anode vanes 6. This scalloping of the anode vanes resulted in excessive localized heating of the anode vanes 6, in use, resulting in catastrophic failure of the tube.

Furthermore the anode wall 19 operates at an elevated temperature, in use, thereby tending to elongate in the axial direction. If this axial elongation is constrained by the tube body, as Was ericountered in the prior design, scalloping of the anode vanes would result from this cause or if the resonators were already slightly scalloped due to the welding operation, previously referred to, the scalloping would be further exaggerated.

By the provsion of the relatively large axial gap 41, Le, 0.051, permitting unrestrained relative axial movement of the anode 19 With respect to the relatively rigid tube body 1, neither the welding operation, during the tube construction, nor the axial expansion of the anode 19 due to its operation at elevated temperatures in use has produced any scalloping of the vanes 6. Tubes constructed in this preferred manner have operated at peak powers of 290 kilowatts, average power 50 watts, at 35 gigacycles. At peak powers of 100 kilowatts and 50 watts average these tubes have operated in excess of 2000 hours without failure.

The axial gap 41 between the free end of anode wall 19 and the tube body 1 including, magnetic pole pieces 12 and the vacuum envelope 1, readily facilitates applying independent operating potentials to the anode structures 6 and 19 relative to the pole pieces 12 and cathode 9. When the pole pieces 12 are operated at the same potential as the cathode 9 the separate cathode end hats 51 of FIG. 4 may be eliminated since their conventional electron beam focusing function is now performed by the pole pieces 12. Removal of the cathode end hats 51 permits the magnetic gap, formed between axially opposed pole pieces 12, to be substantially shortened, as shown in FIG. 5.

The advantage of shortening the magnetic gap is that the magnet size and weight may be reduced accordingly.

For example, a tube as shown in FIG. 4 is characterized by a 0.180" magnetic gap and employs a 20 pound C- shaped magnet. Whereas a tube as shown in FIG. 5, With end hats removed, is characterized by a 0.130 gap and employs a C-shaped magnet weighing less than 10 pounds.

The anode voltage in the alternative structure of FIG. 5 is held oi the cathode and tube body via the intermediary of the axial gap 41 and cylindrical anode insulator 52. Insulator 52 is fixedly secured at one end to the tube body 1 via the intermediary of a metallic annular flange 53. The anode structure 5, 6, 13, 14, 18 and 19, is fixedly carried from the other end of the insulator 52 via transverse metallic header 54 as of copper and shaft 55 as of copper. Vacuum tight seals are made between the tube body 1, flange 53, insulator 52, header 54 and shaft 55 thereby clsing the vacuum envelope. The external end 56 of shaft 55 forrns a terminal for applying the positive anode potential. The cathode 9 is operated at the same potential as the magnet pole pieces 12 and tube body 1. Therefore the cathode standoff insulators 57 of FIGS. 2 and 3 are replaced in FIG. 5 by electrically conductive support cylinders 58 as of a refractory metal.

The axial gap 41 in the output waveguide 2 does not interfere With proper operation of the output structure since the output wave energy is propagating in the TE mode which is characterized by no axially directed currents in the walls of the guide 2. Therefore it is possible to introduce a gap 41 up to of a guide wavelength witl1out deleterious effects. At Ka-band of a guide wavelength is in the order of 0.050 which permits a pulsed anode to tube body voltage of 35 kilovolts.

Since many changes could be made in the above construction and many apparently Widely diiferent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is clamed is:

1. A slot mode absorber apparatus for loading -of undesired slot modes associated Wi-th an array of axially directed elongated slot-s providing Wave energy communication between an array of c -ircumferally spaced anode resonators and a cavity resonator system thmugh a common wall separat-ng the two resonant systems including, a :l-ossy energy absorbing member disposed adjacent and -ooextensively With the end portions of a plurality of said communicating slots, and said energy absorb-ing member being carried directly from the slotted common wall member as an integral unit thereof to move in concert there- With during tube assembly wh ereby as-sernbly of said integral unit is facilitated without introducing distortion into the slotted common wall member.

2. In a cross-field tube apparatus, a cathode, -a11 anode wall With a plurality of vanes extending from one side and defining a plurality =of anode resonators forming a resonant system adjacent to said cat-hode, means defining With said anode wall a oavity resonator, means for coupling alternate ones of said anode resonators to said cavity resonator and including -a plurality of slots communicat-ing through said anode W-all between said anode resonators and said -cavity resonator, means forming a slot mode abs-orber strueture disposed adjacent and coextensive With the end portons of said slots for absorbing energy associated With the resonance of said slots, and means for -carrying said mode absorber from said anode wall as an integral unit thereof where-by assembly of said integral anode wall and mode absorber structure is faeilitated without introducing distortion into said slotted anode wall.

3. A reverse magnetron tube apparatus including a body portion forming a hollow structure cap-able of evacuation, ar1 inner cavity resonator for sustaining the TE mode of oscillation and hav-ing an outer cy-lindrical side wall, a plurality of anode resonators surrounding said eylindrical outer wall, means for locking the 1r mode of oscillation of said plural-ity of anode resonators to said TE mode of said inner cavity resonator, said looking means ineluding a circumferential array of axially directed slots extend-ing through said cylindrical outer side wall member and com-munieat-ing With alternate ones of said anode resonators, a ring of lossy material disposed -adjacent the end portions f said slots on the outside of said outer cylindrical wall for loading modes of oscillation 0f said slots, a channel member serving to affix said ring of lossy material to said outer cyliudrical side wall by capturing said ring and cylindrical side wall between the two leg porti-ons of said channel whereby said lossy ring is aflxed to said cylindrical side wall as an integral unit thereof for facilitatng assembly of said unit without introducing distortion into said slotted side wall.

4. In a crossed-fieid tube apparatus, a cathode, an anode wall With a plurality of anode resonators formed on the side adjacent to said cathode and defining a resonant system, means defining With said anode wall a cavity resonator, means for wave energy coupling alternate ones of said anode resonators to said cav-ity resonator and ineluding a plurality of slots communicating through said anode wall between said anode resonators and said cavity resonator, means forming 2. slot mode absorber element positioned at least at one end of said slots and beng juxtapositioned the end portions of said slots for -suppression of undesired resonant modes of oscillation of said slots, and said slot mode absorber element extending in the direction -of said anode wall toward said anode resonators from the ends of said slots, and the thickness of said mode absorber element taken in the direction perpendicular to said anode wall decreasing in the direction toward said anode resonators, whereby coupling to the electric fields of said anode resonators by said lossy mode absorber is minimized in use.

5. A reverse magnetron tube apparatus including, an evacuable tubular body portion, a cylindrical anode wall with a plurality of vanes extending from one side thereof and defining a plurality of anode resonators, a cathode structure surrounding said anode resonators and being disposed adjacent thereto and defining a magnetron interaction region inbetween said anode resonators and said cathode, means defining with said cylindrical anode wall a cavity resonator, a circurnferential array of axially directed coupling slots communicating through said cyl-indrical anode wall to a. plurality of said vane anode resonators for coupling alternate ones of said anode resonators to said cavity resonator, Ineans fixedly securing said cylindrical anode wall to said tube envelope substantially only at one end of said cylindrical anode wall, whereby substantially unrestrained axial translation of said cyliudrical anode Wa'l1 -is permitted relative to said tubular envelope structure at the other end of said anode wall to prevent compression of said cyliudrical anode wall, in use, with consequent deformation of said anode resonators.

6. In a crossed-field apparatus, a cathode structure, an anode structure forming a wave propaga-ting structure juxtapositioned said cathode in substantial coaxial relationship therewith, a tube envel-ope body structure enveloping said cathode and anode structure, a circular electric mode waveguide coaxially aligned with said wave propagating structure for coupling wave energy from said structure to a load, means for fixed1y connecting said anode structure to said envelope structure substantiaily only from one axial end of said anode structure, and said circu1ar electric mode waveguide having un axia1 gap formed in the side wall thereof between said anode structure and said waveguide for permitting said anode structure to be 0perated at a potential independent of said circular electric mode Waveguide and said envelope structure.

7. A reverse magnetron tube apparatus including, an evacuable ho1low body structure, a cylindrical anode wall having a plurality of vanes extending from one side thereof and defining an anode wave propagating structure, a cathode structure surrounding said anode wave propagating structure and being disposed adjacent thereto and defining a magnetron interaction region =inbetween said anode wave supporting structure and said cathode, means defining With said cylindrical anode wall a circu- 1ar electric mode -cavity resonator, a circumferral array of axially directed coupling slots communicating through said cylindrical anode wall to said anode Wave supporting structure for coupling said anode wave supporting structure to said cavity resonator, a circular electric mode waveguide axially aligned With said circular electric mode cavity in wave energy communication therewith, means fixedly securing said cylindrical anode wall to said tube body substantially only from a first end of said cylindrical anode wall, and said circular electric mode waveguide being spaced from the second end of said cylindrical anode wall to define an annular gap therebetween for permitting said anode wall to be operated at a potential independent of said circular electric mode waveguide and said evacuable tube body.

8. The apparatus according to claim 7 wherein said -rneans for fixedly securing said cylindrical anode wall frorn sa-id first end thereof to said tube body includes an insulator member interconnecting said anode and tube body members.

9. The apparatus according to claim 8 wherein said annular gap is formed in the side wall of said circular electric mode waveguide inbetween the second end of said cylindrical anode wall and said circular electric mode waveguide, and said gap having an axial Iength less than one-tenth of a guide wavelength at the center operating frequency of the tube apparatus.

Refereuces Cited by the Examiner UNIT ED STATES PATENTS 2,567,210 9/1951 Hupcey 333-22 2,678,407 5/1954 Brown et al 315-39.51

2,901,666 8/1959 Sixsmth 315-39.51

FOREIGN PATENTS 1,167,523 8/1958 France.

GEORGE N. WESTBY, Primary Examimzr.

DAVID I. GALVIN, Examz'ner. 

1. A SLOT MODE ABSORBER APPARATUS FOR LOADING OF UNDESIRED SLOT MODES ASSOCIATED WITH AN ARRAY OF AXIALLY DIRECTED ELONGATED SLOTS PROVIDING WAVE ENERGY COMMUNICATION BETWEEN AN ARRAY OF CIRCUMFERALLY SPACED ANODE RESONATORS AND A CAVITY RESONATOR SYSTEM THROUGH A COMMON WALL SEPARATING THE TWO RESONANT SYSTEMS INCLUDING, A LOSSY ENERGY ABSORBING MEMBER DISPOSED ADJACENT AND COEXTENSIVELY WITH THE END PORTIONS OF A PLURALITY OF SAID COMMUNCATING SLOTS, AND SAID ENERGY ABSORBING MEMBER BEING CARRIED DIRECTLY FROM THE SLOTTED COMMON WALL MEMBER AS AN INTEGRAL UNIT THEREOF TO MOVE IN CONCERT THEREWITH DURING TUBE ASSEMBLY WHEREBY ASSEMBLY OF SAID INTEGRAL UNIT IS FACILITATED WITHOUT INTRODUCING DISTORTION INTO THE SLOTTED COMMON WALL MEMBER.
 5. A REVERSE MAGNETRON TUBE APPARATUS INCLUDING, AN EVACUABLE TUBULAR BODY PORTION, A CYLINDRICAL ANODE WALL WITH A PLURALITY OF VANES EXTENDING FROM ONE SIDE THEREOF AND DEFINING A PLURALITY OF ANODE RESONATORS, A CATHODE STRUCTURE SURROUNDING SAID ANODE RESONATORS AND BEING DISPOSED ADJACENT THERETO AND DEFINING A MAGNETRON INTERACTION REGION INBETWEEN SAID ANODE RESONATORS AND SAID CATHODE, MEANS DEFINING WITH SAID CYLINDRICAL ANODE WALL A CAVITY RESONATOR, A CIRCUMFERENTIAL ARRAY OF AXIALLY DIRECTED COUPLING SLOTS COMMUNICATING THROUGH SAID CYLINDRICAL ANODE WALL TO A PLURALITY OF SAID VANE ANODE RESONATORS FOR COUPLING ALTERNATE ONES OF SAID ANODE RESONATORS TO SAID CAVITY RESONATOR, MEANS FIXEDLY SECURING SAID CYLINDRICAL ANODE WALL TO SAID TUBE ENVELOPE SUBSTANTIALLY ONLY AT ONE END OF SAID CYLINDRICAL ANODE WALL, WHEREBY SUBSTANTIALLY UNRESTRAINED AXIAL TRANSLATION OF SAID CYLINDRICAL ANODE WALL IA PERMITTED RELATIVE TO SAID TUBULAR ENVELOPE STRUCTURE AT THE OTHER END OF SAID ANODE WALL TO PREVENT COMPRESSION OF SAID CYLINDRICAL ANODE WALL, IN USE, WITH CONSEQUENT DEFORMATION OF SAID ANODE RESONATORS. 